Catalyst regeneration and multicycle growth of high purity and yield semiconducting single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) with specific electrical types are urgently demanded for future nanoelectronic applications. However, it is still a challenge to simultaneously improve the purity and yield of semiconducting SWCNTs (s-SWCNTs). Herein, we propose a new multicycle approach to directly synthesize s-SWCNTs by chemical vapor deposition (CVD) using Fe_0.01Mg_0.99O as catalyst regeneration host. The appropriate carbon feedstock used in the first-time growth is CH₄. During this process, the lattice oxygen would be released from Fe_0.01Mg_0.99O catalyst through H₂ reduction and then form water vapor. The water vapor could in-situ selectively etch metallic SWCNTs (m-SWCNTs) in the nucleation process. After the termination of the first-time growth stage, the deactivative catalyst was regenerated by oxidation treatment, then it was reused to grow SWCNTs again. Carbon feedstock was changed to C₂H₅OH for the multicycle growth of SWCNTs and the secondary etching of as-grown m-SWCNTs and smaller-diameter SWCNTs. The selective synthesis of s-SWCNTs through this new multicycle growth process was up to 93.2% abundance, and the yield of SWCNTs was improved from 0.76% to 1.34% (weight ratio to the catalyst powder). It is interesting that there exists a diameter threshold value, which could affect the ∙OH groups etching on m-SWCNTs. According to the DFT simulation, the experimental results are related to the absorption capacity and reaction activity of SWCNTs. It presents a new approach to the massive synthesis of high purity s-SWCNTs and has wide applications in the future.